The present invention relates generally to surgical instruments, and more particularly to methods and devices for improved tissue stabilization using multiple link support members. The tissue stabilizers described herein are particularly useful for stabilizing the beating heart during coronary artery bypass graft surgery.
A number surgical procedures require the surgeon to perform delicate operations on tissues within the body that are moving or otherwise unstable. For example, surgeons are routinely performing successful coronary artery bypass graft surgery (CABG) on the beating heart. In a typical coronary artery bypass graft procedure, a blocked or restricted section of coronary artery, which normally supplies blood to a portion of the heart, is bypassed using a source vessel or a graft vessel to re-establish blood flow to the artery downstream of the blockage. This procedure requires the surgeon to create a fluid connection, or anastomosis, between the source or graft vessel and an arteriotomy or incision in the coronary artery. Anastomosing two vessels in this manner is a particularly delicate procedure requiring the precise placement of tiny sutures in the tissue surrounding the arteriotomy in the coronary artery and in the source or graft vessel so that the two may be sutured together.
To ensure that the sutures may be placed with the required accuracy and precision to yield an anastomosis having the desired long term patency, a number of devices have been developed to stabilize a portion of the heart in the vicinity of the target coronary artery. The vast majority of devices suitable for successfully stabilizing the beating heart use either compression or vacuum, or both, to engage and immobilize a portion of cardiac tissue, preferably along opposite sides of the target artery. Devices configured to use a compressive force to stabilize a surgical site on the beating heart can be found, for example, in U.S. Pat. No. 5,894,843 to Benetti et al. Examples of devices configured to use negative pressure or vacuum to stabilize or to assist in stabilizing cardiac tissue are described, for example, in U.S. Pat. No. 5,727,569 to Benetti et al. and U.S. Pat. No. 5,836,311 to Borst et al.
The devices used to stabilize the beating heart must be sufficiently stiff or rigid to resist or placate the movement of the still beating heart muscle as it contracts and relaxes in regular fashion to pump blood throughout the body. Such stabilization devices typically employ a tissue engaging or contacting member and some type of support member to connect the tissue contacting member to a stable support, such as a properly constructed rib or sternal retractor. The support member is most often either a continuous substantially rigid straight or curved shaft or a multiple link member that is sufficiently flexible for positioning and which can be made substantially rigid for stabilization.
Multiple link members typically involve a series of in-line ball and socket links which may be forced together axially by way of a wire or cable extending generally through the center of each link. As the links are forced together, the frictional forces between the successive links increase in proportion to the axial forces supplied by the cable until the frictional forces within the successive ball and socket links along the support member become so great as to resist relative movement therebetween, thus rendering the support member substantially rigid. Examples of articulating members having a plurality of links can be found in European Patent Application EP 0 803 228 A1 published on Oct. 29, 1997 and U.S. Pat. No. 5,899,425.
While the simple operation of multiple link devices have found some acceptance as suitable support members for use in connection with tissue stabilizers, it has proved very difficult to produce the required rigidity and maneuverability required in certain demanding surgical applications, such as stabilizing the beating heart during a CABG procedure. Regarding the rigidity of multiple link devices, for example, a great deal of axial force must be generated to ensure each of the links become sufficiently locked to resist any motion at the surgical site. To support these high loads, the links typically have a much greater diameter than their continuous shaft alternatives thus occupying a greater amount of space in the surgical field.
In addition, the ability to maneuver and position the distal end of a multiple link support member as desired within the surgical field is disadvantaged by the limited range of motion available between successive links along the support member. Attempting to position device through tight turns often proves excessively difficult. For example, a multi-link device may allow each link to rotate only about 15 degrees relative to an adjacent link. With such a configuration, articulating the support member through a 90 degree turn may involve six or more links, thus occupying an excessive amount of space in or near the operative field and resulting in a relatively large radius curve.
Because the rigidity is somewhat inefficient, requiring an increased device size and high forces, and because the maneuverability is limited by the relatively small range of motion between adjacent links, it can be quite difficult to reach and stabilize vessels of the beating heart which are remote from the access opening established by the retractor. Multiple link support members may be unable to develop the rigidity required for optimum stabilization of the peripheral arteries of the beating heart and may be difficult to position at the remote locations which require tight turns or extreme angles of the support member or the contacting member relative to the support member.
Further, when the proximal end of the support member is attached to the retractor in a generally horizontal orientation, it is difficult for a multiple link support member to maneuver the initial roughly 90 degree or less turn required to position the distal end vertically down into the target surgical site. If the multiple link support member is unable to form a sufficiently tight turn or angle relative to its attachment to the retractor, it will tend to occupy an excessive amount of space at the access opening thus blocking visual and instrument access to the target surgical site to be stabilized.
In view of the foregoing, it would be desirable to have a tissue stabilizing device having a tissue contacting member and support member for stabilizing the beating heart which maintains the simplicity of use inherent to multiple links systems but also provides improved maneuverability and rigidity for optimum stabilization. It would also be desirable to have a multiple link support member having a proximal joint or mount which facilitates a sharp turn or angle, such as may be required when the support member is connected proximally to a retractor or other such device.
The present invention will be described primarily for use during CABG surgery, but the invention is not limited thereto, and is contemplated to be useful for other surgical procedures as well.
The devices and methods of the present invention involve tissue stabilizers which are constructed to provide superior maneuverability and improved tissue stabilization at a target site, for example on the beating heart. The present invention may involve stabilization devices that use at least one multiple link support member to operably connect a stabilizer foot to a stable support, such as a retractor. To minimize motion at the stabilizer foot and improve the overall stabilization of a target site, the present invention may involve a stabilizer foot having two or more multiple link support members. The stabilizer foot is typically positioned as desired at the surgical site with at least one support member connecting the stabilizer foot to a stable support. Subsequently, one or more additional support members may be provided and connected to the stabilizer foot, typically at different locations, to obtain optimum stabilization.
One aspect of the present invention involves an apparatus for stabilizing a coronary artery on a patient""s heart comprising a stabilizer foot adapted to engage the surface of the heart, a first support member, and a second support member. The first support member may have a distal end connected to the stabilizer foot at a first distal articulating joint and a proximal end connected to a stable support at a first proximal articulating joint. The second support member preferably has a distal end connected to a second distal articulating joint and a proximal end connected to a stable support at a second proximal articulating joint. The present invention may involve third and, if desired, fourth support members each having separate distal and proximal attachments. Having more than one support member connecting to the stabilizer foot and the stable support at different locations provides greatly improved stabilization.
The stabilizer foot may be configured to have a variety of different distal articulating joints including pinned or rotational joints, ball joints, malleable joints, or the like. In a preferred embodiment, the first or second distal articulating joint is a ball and socket joint, typically formed between a ball or ball-shaped member extending from the stabilizer foot and a mating cavity formed within the most distal link of the first or second support member. The first and second distal articulating joint may also be a rotational joint, typically formed between a generally cylindrical post extending from the stabilizer foot and a mating cylindrical surface provided within the most distal links of the first or second support member. Preferably, the first distal articulating links is a ball and socket joint allowing optimum positioning of the stabilizer foot against the beating heart and the second distal articulating links is a simple rotational joint that facilitates quick attachment of the second support member to the stabilizer foot.
Preferably, the first support member includes a distal link, a proximal link, and a plurality of interconnecting links therebetween. Each of the interconnecting links preferably has a ball or ball-shaped end and a socket or socket-shaped end. The ball shaped ends of the interconnecting links are cooperatively engaged with the socket shaped ends of adjacent interconnecting links thereby forming articulating ball joints between adjacent interconnecting links in a manner that allows the first support member to articulate to varied positions, shapes, or orientations along its length.
Each of the interconnecting links preferably has a central hole through which a flexible wire or cable may be routed. The cable has a distal end connected to the distal link and is routed through the central hole of each of the interconnecting links, preferably exiting through the proximal link. Applying a tensile force to the proximal end of the cable frictionally locks the articulating ball joints between adjacent interconnecting links, thereby causing the support member to become relatively rigid.
The resulting force distribution amongst the multiple support members allows the support members to be configured with relatively small cross-sectional profiles even when the lengths of the support members are quite long. For example, the first support member preferably has a length of greater than about 6.5 inches and an average diameter of less than about 0.5 inches. More preferably, the first support member has a length of about 7.0 inches to about 9.0 inches. The smaller profiles and longer lengths advantageously provide the surgeon with greater visual and instrument access to the surgical site.
The stabilizer foot itself may be adapted to engage the surface of the heart using negative pressure, for example, by way of a vacuum chamber or by way of a plurality of vacuum ports. More preferably, the stabilizer foot has at least one contact surface, preferably textured or otherwise adapted to frictionally engage the surface of the heart. In a preferred embodiment, the stabilizer foot has a first contact surface and a second contact surface, the second contact surface being spaced apart from and oriented substantially parallel to the first contact surface.
Typically, the first and second contact surfaces will be positioned on opposite sides of the target coronary artery. The stabilizer foot may have first and second posts extending about the first and second contact surfaces to which third and fourth support members may be connected. The third and fourth support members have proximal ends connected to the stable support at third and fourth proximal articulating joints, respectively. Preferably, the stable support is a sternal or rib retractor but may be any other stable structure.
Another aspect of the present invention involves an apparatus for stabilizing a coronary artery on a patient""s heart which includes a retractor, a mount base operably connected to the retractor, a mount body connected to the mount base at a first articulating joint along a first axis, a multiple link support member, and a stabilizer foot. The proximal end of the support member is preferably operably connected to the mount body along a second axis. The stabilizer foot may be operably connected to the distal end of the support member and adapted to engage the surface of the heart, for example, using friction or negative pressure.
In a preferred embodiment, the first axis is at an angle relative to the second axis, the angle being between about 120 degrees and about 45 degrees, more preferably the angle being about 90 degrees. This dual axis articulation allows optimum access and positioning of the stabilizer foot and support member within the surgical field.
The retractor preferably has opposing retractor blades adapted to engage opposite sides of an access incision. In a preferred embodiment, at least one of the retractor blades further comprises a rail. Preferably, the rail has first and second rail tabs extending therefrom along the length of the rail. Preferably, the mount base is adapted to engage the retractor blade at any desired position along the rail. In a preferred embodiment, the mount base has first and second channels sized to engage the rail tabs. The second channel may be moveable relative to the first channel such that the first and second channels slidably engage the rail tabs when the second channel is in a first position and the channels frictionally grip the rail tabs when the second channel is in a second position.
In a preferred embodiment, the multiple link support member comprises a distal link a proximal link and a plurality of interconnecting links therebetween. Each of the interconnecting links may have a ball or ball-shaped end and a socket-shaped end, the ball-shaped ends being cooperatively engaged with the socket-shaped ends of adjacent interconnecting links thereby forming articulating ball joints between interconnecting links. The distal link preferably has a mating cavity adapted to receive a ball-shaped member extending from the stabilizer foot.
Another aspect of the present invention involves an apparatus for stabilizing the coronary artery which involves a stabilizer foot adapted to engage the surface of the beating heart and a multiple links support member having a proximal end link, a distal end link, and a plurality of center links arranged end-to-end therebetween. The support member preferably has a cable extending through the center links. In a preferred embodiment the distal end link comprises a first member and a second member, the second member having at least first and second portions defining a cavity therebetween for receiving the ball-shaped member. The first member may have a bearing surface adapted to engage at least a portion of the second member to urge the first and second flexible portions together against the ball-shaped member.
The first member preferably has a bore adapted to receive at least a portion of the second member. The distal end of the cable is attached to the second member such that when the second member is pulled in a direction towards the first member by operation of the cable, the first and second flexible portions are engaged by the bearing surface causing them to frictionally engage the ball-shaped member with sufficient force the position of the stabilizer foot relative to the distal end link. In one embodiment, the bearing surface is frustoconical.
The proximal end of the support member is preferably attached to a stable support, which in a preferred embodiment comprises a retractor having opposing retractor blades for engaging opposite sides of an access incision. The stabilizing apparatus may further include a mount base operably connected to the retractor and a mount body connected to the mount base at a first articulating joint along a first axis. The proximal end link is preferably connected to the mount body along a second axis. The first axis may be angled relative to the second axis, the angle being between about 120 degrees and about 45 degrees.
Another aspect of the present invention involves a method for stabilizing a coronary artery on a patient""s heart which may comprise the steps of creating an access opening into the patient""s thoracic cavity to gain access to the beating heart, providing a stabilizer device having a stabilizer foot operably connected to a support member having a flexible condition and a relatively rigid condition, with the support member in a flexible condition, positioning the stabilizer foot to engage the surface of the heart adjacent the coronary artery, causing the support member to assume the relatively rigid condition to thereby resist movement of the stabilizer foot, providing at least one additional support member, attaching the distal end(s) of the additional support member(s) to the stabilizer foot, and causing the additional support member(s) to assume a relatively rigid condition to thereby provide additional resistance against movement of the stabilizer foot. The access opening is preferably created using a retractor and the method may further include the step of attaching the support member and the additional support member(s) to the retractor.
These and other features of the present invention will become more fully apparent from the following description and appended claims.